U.S. patent number 6,558,154 [Application Number 09/987,128] was granted by the patent office on 2003-05-06 for burner system with staged fuel injection and method for its operation.
This patent grant is currently assigned to Alstom (Switzerland) Ltd. Invention is credited to Adnan Eroglu, Hans Peter Knoepfel, Christian Oliver Paschereit, Peter Stuber.
United States Patent |
6,558,154 |
Eroglu , et al. |
May 6, 2003 |
Burner system with staged fuel injection and method for its
operation
Abstract
A burner system with staged fuel injection includes a burner
with a swirl generator (1) for a combustion air stream and
device(s) for introducing fuel into the combustion air stream,
wherein the fuel introducing devices include at least two separate
fuel supply elements (4a, 4b) with groups of fuel outlet openings
for corresponding premix fuel amounts, wherein a first group is
arranged downstream from a second group. The burner system
furthermore includes measurement value probes (8, 9) for measuring
the pulsations and emissions of the combustion, as well as a
control device (10) that controls the two stages (4a, 4b) for
introducing fuel dependent on the measured measuring values. The
burner system permits optimized operation of the system even under
changing operating and environmental conditions.
Inventors: |
Eroglu; Adnan (Untersiggenthal,
CH), Stuber; Peter (Zurich, CH),
Paschereit; Christian Oliver (Baden, CH), Knoepfel;
Hans Peter (Dottikon, CH) |
Assignee: |
Alstom (Switzerland) Ltd
(Baden, CH)
|
Family
ID: |
7663077 |
Appl.
No.: |
09/987,128 |
Filed: |
November 13, 2001 |
Foreign Application Priority Data
|
|
|
|
|
Nov 13, 2000 [DE] |
|
|
100 56 124 |
|
Current U.S.
Class: |
431/8; 431/351;
431/354; 431/75; 60/737; 60/748 |
Current CPC
Class: |
F02C
9/28 (20130101); F23R 2900/00013 (20130101) |
Current International
Class: |
F02C
9/28 (20060101); F02C 9/00 (20060101); F23C
005/00 () |
Field of
Search: |
;431/1,8,10,75,173,284,350-354,347 ;60/737,748,743,733 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
4040745 |
|
Jul 1991 |
|
DE |
|
4339094 |
|
May 1995 |
|
DE |
|
4446842 |
|
Jul 1996 |
|
DE |
|
4446945 |
|
Jul 1996 |
|
DE |
|
19636093 |
|
Mar 1998 |
|
DE |
|
0321809 |
|
May 1991 |
|
EP |
|
0780629 |
|
Jun 1997 |
|
EP |
|
0881373 |
|
Dec 1998 |
|
EP |
|
0962704 |
|
Dec 1999 |
|
EP |
|
0985810 |
|
Mar 2000 |
|
EP |
|
2306216 |
|
Apr 1997 |
|
GB |
|
93/17279 |
|
Sep 1993 |
|
WO |
|
Primary Examiner: Yeung; James C.
Attorney, Agent or Firm: Burns, Doane, Swecker & Mathis,
L.L.P.
Claims
What is claimed is:
1. A burner system with staged fuel injection, comprising: a burner
having a swirl generator for a combustion air stream and means for
introducing fuel into the combustion air stream, the means for
introducing fuel into the combustion air stream comprising at least
one first fuel supply means with a first group of fuel outlet
openings for a first premix fuel amount and a second fuel supply
means with a second group of fuel outlet openings downstream from
the first group of fuel outlet openings for a second premix fuel
amount; at least one probe selected from the group consisting of a
first measuring value probe that measures combustion pulsations
initiated by the burner, a second measuring value probe that
measures emission values, and both and a control device connected
to the at least one probe to receive the measuring data from the at
least one probe, and connected to the first and second fuel supply
means to control the fuel supply based on the measuring data
provided by the at least one probe.
2. A burner system as claimed in claim 1, wherein the control
device comprises control data stored in a memory and logic for
comparing the data provided by the at least one probe with the
control data, the logic providing control signals for controlling
the fuel supply via the first and second fuel supply means.
3. A burner system as claimed in claim 1, further comprising: at
least one control valve; a supply line for each of the first and
second fuel supply means, the at least one control valve regulating
the fuel supply through the supply lines.
4. A burner system as claimed in claim 3, wherein the at least one
control valve is in communication with and controlled by the
control device.
5. A burner system as claimed in claim 3 wherein the supply line
for the second fuel supply means branches off the supply line for
the first fuel supply means.
6. A burner system as claimed in claim 5, wherein the at least one
control valve comprises a control valve controlled by the control
device for distributing the fuel amount between the supply
lines.
7. A burner system as claimed in claim 1, wherein the burner has a
burner axis, and the first and second group of fuel outlet openings
on the swirl generator are arranged in the direction of the burner
axis.
8. A method for operating a burner with staged fuel injection, the
burner being provided with at least one first stage and one second
stage arranged downstream from the first stage for the introduction
of fuel into a combustion air stream, comprising the steps of:
measuring at least one value selected from the group consisting of
pulsations of combustion initiated by the burner, emission values
of the combustion, and both; and controlling the fuel supply to the
first and second stage based on the value measured in the measuring
step.
9. A method as claimed in claim 8, wherein the step of controlling
the fuel supply comprises controlling the fuel supply to the first
and second stage to minimize the pulsation values, the emission
values, or both.
10. A method as claimed in claim 8, wherein the step of controlling
comprises controlling the fuel supply with control valves provided
in the supply lines for the first stage and the second stage.
11. A method as claimed in claim 8, wherein the step of controlling
comprises controlling the fuel supply with a control valve that
controls the division of the fuel between the supply lines of the
first and second stages.
12. A method as claimed in claim 8, wherein the step of controlling
comprises comparing the at least one value to predetermined control
data which shows a dependence of the pulsations, the emission
values, or both, on the fuel supply to the first and second
stage.
13. A method as claimed in claim 12, wherein the step of
controlling comprises controlling the fuel supply during stationary
operation so that the operating point is below the maximum of the
pulsations.
14. A method as claimed in claim 11, wherein the step of
controlling comprises controlling the fuel supply during transient
operation so that the operating point is above the maximum of the
pulsations.
Description
FIELD OF THE INVENTION
The invention at hand relates to a burner system with staged fuel
injection as well as an operating method associated with it. The
burner system includes a burner with a swirl generator for a
combustion air stream and means for introducing fuel into the
combustion air stream, whereby the means for introducing fuel into
the combustion air stream includes at least one first fuel supply
means with a first group of fuel outlet openings for a first premix
fuel amount and a second fuel supply means with a second group of
fuel outlet openings downstream from the first group of fuel outlet
openings for a second premix fuel amount. A preferred field of
application for such a burner system is the gas and steam turbine
technology.
BACKGROUND OF THE INVENTION
EP 0 321 809 B1 discloses a conical burner having several shells, a
so-called double-cone burner. The conical swirl generator composed
of several shells produces a closed swirl flow in the cone head,
which, based on the increasing swirl, becomes instable along the
cone tip and changes into an annular swirl flow with backflow in
the core. The shells of the swirl generator are configured in such
a way that tangential air inlet slits for the combustion air are
formed along the burner axis. Along the cone shells' inflow edge
created by this, supply means for the premix gas, i.e., the gaseous
fuel, are provided, which have outlet openings for the premix gas
distributed in the direction of the burner axis. The gas is
injected transversely to the air inlet slit through the outlet
openings or holes. In connection with the swirl of the combustion
air/combustion gas flow generated in the swirl chamber, this
injection results in a good mixing of the combustion or premix gas
with the combustion air. In such premix burners, a good mixing is
the prerequisite for low NO.sub.x values during the combustion
process.
In order to further improve on such a burner, EP 0 780 629 A2
discloses a burner for a heat generator provided after the swirl
generator with an additional mixing section for mixing fuel and
combustion air. This mixing section, for example, could be realized
as a subsequent pipe, into which the flow exiting the swirl
generator is guided without any significant flow losses. This
additional mixing section makes it possible to further increase the
mixing efficiency and therefore to reduce noxious emissions.
FIG. 1 schematically shows an example for such burners, in which
the fuel is mixed with the inflowing combustion air via outlet
openings in supply channels arranged along the burner axis in the
swirl body 1. The figure hereby shows the conical swirl body 1 of
the burner, on or in which the fuel supply means with outlet
openings 2 arranged along the burner axis--shown in the figure by
arrows symbolizing the injected fuel--extend. These fuel supply
means usually are constructed as single channels with a fixed
distribution of the fuel outlet openings 2 along the burner axis.
The figure also shows a pilot lance 3, through which the fuel is
injected directly into the swirl chamber during the start-up of the
burner. With an increasing load, a switchover from this pilot stage
to the premix operation occurs, in which the fuel is mixed via the
mentioned fuel outlet openings 2 with the inflowing combustion
air.
Another known burner geometry of a premix burner is known from WO
93/17279. This arrangement uses a cylindrical swirl generator with
an additional, conical internal body. The premix gas is also
injected via supply means with corresponding outlet openings into
the swirl chamber, the outlet openings being arranged along the
axially extending air inlet slits. The pilot supply means of this
burner is provided at the end of the conical internal body. The
pilot operation results in increased NO.sub.x emissions, however,
since this type of operation only allows an insufficient mixing
with the combustion air.
All known burner systems are designed with a single-stage supply of
the fuel during premix operation. Size, distribution, arrangement,
spacing, as well number of the outlet openings of the fuel supply
means along the burner axis must be optimized in order to fulfill
the requirements regarding low emissions, extinction limit,
backflash limit, as well as requirements for combustion stability.
It is hereby almost impossible to also fulfill all of these
requirements with a fixed distribution of the outlet openings under
changing operating and environmental conditions. The characteristic
of injection with respect to penetration depth and mixing-in of the
gas jets as well as the fuel distribution along the air inlet slits
or burner axis are established by the selection of the
aforementioned parameters. A distribution of the outlet openings
that are optimized for a particular type of system, for example
with a ring combustion chamber, is no longer optimized for another
type of system, for example one with a silo combustion chamber.
Furthermore, the operating conditions of a system change over time,
for example because leakage currents increase as a result of aging
effects. A fixed distribution of the outlet openings is unable to
compensate for such aging effects.
Another advantage of the known methods for operating premix burners
is that they are optimized for low emissions and low combustion
oscillations under full load conditions. An additional pilot stage
is necessary for starting up the burner and gas turbine. At a
certain operating load, at which the combustion can be maintained
in premix operation, the burner is switched from the pilot to the
premix stage. In the same manner, the shutting down of the gas
turbine requires a switchover from premix operation to pilot
operation. However, these switching processes cause strong
combustion oscillations as well as large load oscillations. They
furthermore require large amounts of an inert gas in order to flush
the fuel supply means that are no longer in operation after the
switchover. This is necessary in order to avoid an ignition of the
unused fuel supply means through circulating hot gases.
Switchover processes from liquid to gaseous fuel, or vice versa,
are also difficult to realize using existing fuel injection
techniques because of the proximity of the injection nozzles to the
inlet openings of the pilot system.
An aspect of the invention is a burner system as well as a method
for operating a burner that do not have the above disadvantages and
also permit optimized operation with changing operating and
environmental conditions.
SUMMARY OF THE INVENTION
The burner system according to the invention includes a burner with
a swirl generator for a combustion air stream and means for
introducing fuel into the combustion air stream, whereby the means
for introducing fuel into the combustion air stream includes at
least one first fuel supply means with a first group of fuel outlet
openings for a first premix fuel amount (first stage) and a second
fuel supply means with a second group of fuel outlet openings
(second stage) downstream from the first group of fuel outlet
openings for a second premix fuel amount. Naturally, further groups
of fuel outlet openings for further premix fuel amounts can be
provided independently from the first and second group.
Furthermore, several first and second fuel supply means for the
respective stage are usually distributed with their outlet openings
over the circumference of the swirl body, as is known already from
the single-phased systems. The burner system also comprises a first
measuring value probe that measures pulsations of a combustion
initiated by the burner, and/or a second measuring value probe that
measures the emission values of the combustion. The measuring value
probes are connected to a control device that receives the
measuring data from the measuring value probe(s) and controls the
fuel supply by way of the first and second fuel supply means--as
well as, if applicable, other fuel supply means--dependent on the
measuring data provided by the measuring value probe(s). The
control therefore adheres to the desired specifications. Naturally,
more than one measuring value probe can be used to measure the
pulsations and/or emission values.
In the simplest case of such a burner system, all or several of the
fuel supply means arranged at the swirl body, in the case of
single-stage systems, are divided into at least two independent
channels for the fuel in order to form the different stages.
Naturally, several juxtaposed fuel supply means can be provided, in
which the outlet openings are offset from each other along the
longitudinal axis in such a way as to form the separate stages. The
skilled artisan will recognize many ways available for providing
different groups of outlet openings on the swirl body along the
burner axis, where said groups can be supplied with fuel
independently from each other. The fuel supply to the individual
stages is controlled or regulated via the control device according
to the aforementioned specifications, dependent on the pulsations
and/or emission values. Preferably, this is accomplished with
control valves provided in the supply lines to the first and second
fuel supply means.
Suitable measuring value probes that can be provided in the flame
region--in order to measure the pulsations--or at the outlet of the
burner--in order to measure the emission values--are known to the
expert. Numerous sensors for measuring the emissions and, as a
rule, acoustic sensors for measuring the pulsations, are available
for this purpose.
The control of the fuel supply means by way of the control device
is performed preferably by means of comparative data stored in a
memory of the control device. The control device compares the
measured data with the control data in order to be able to
determine the current operating point of the burner system and
control the fuel supply in towards the desired operating point.
Compared with single-stage burner systems, the use of a burner
system with staged fuel injection permits a clearly expanded
operating range. With a suitable arrangement of the supply lines to
the fuel supply means of the individual stages, this does not
require any additional, separate fuel cycle. The independent
controllability of the at least two stages of the burner system in
connection with the control device permit an operation with low
pulsations from ignition to basic load as well as low NO.sub.x
emissions. No pilot stage is required for this burner system, so
that also no switchover processes with the associated pulsations or
load oscillations occur. The operation of the burner system does
not require flushing with inert gases, such as, for example,
N.sub.2. This at the same time reduces the operating costs of the
system. The absence of the pilot stage also makes it possible to
realize a simpler switchover from fuel oil to fuel gas operation
and vice versa.
A special advantage of the burner system of the present invention
is the dynamic controllability via the control device, whereby an
optimum operating point can be realized for every type of system,
every environmental condition, every age, and every degree of
leakage. In particular, this operating point can be continuously
adapted dependant on the mentioned parameters during operation of
the system. The burner system as well as the associated operating
method therefore permits optimum operation of the system under
changing operating and environmental conditions.
In a preferred embodiment of the present burner system, the supply
line to the fuel supply means of the second stage branches off the
first stage--or vice versa. In this case, the burner system only
can be controlled by controlling a control valve that influences
the distribution of the fuel amount to the two fuel supply means.
With a specified total fuel supply, this means that the
distribution between the two stages is controlled via this valve.
The control device hereby is connected only with this valve.
In the preferred type of operation of the present burner system,
the fuel supply to the first and second stage is controlled in such
a way as to minimize the pulsations and emission values. The
control is preferably accomplished by a comparison with control
data stored in the control device that were determined during prior
testing and that show a dependence between the pulsations and
emission values and the fuel supply to the first and second stage
or the fuel distribution between the first and second stage. Here
also it is naturally possible to operate more than two stages in
the same manner.
A very good operating behavior is found when, during stationary
operation, the fuel supply is controlled in such a way that the
operating point is below the maximum of the pulsations--dependant
on the fuel supply to the first stage--and in the case of a
transient operation is above the maximum of the pulsations.
Although the present patent application does not give a detailed
description of the exact size of the outlet openings, their
arrangement, their spacing, and their distribution, the skilled
artisan will not have a problem in finding suitable geometries and
distributions. This may be accomplished simply by realizing the
outlet openings provided in existing single-stage burners on the
swirl body along the burner axis also in the same way for the
present burner system, whereby the fuel supply means channel hereby
must only be divided into parts that form the first and second
stage. The skilled artisan will be aware of possibilities for
optimizing or adapting the distribution of the outlet openings from
single-stage burners.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention shall briefly be described below again with
the help of exemplary embodiments in reference to the drawings
without restricting the general concept of the invention, in
which:
FIG. 1 shows a single-stage burner system according to the state of
the art;
FIG. 2 shows a schematic illustration of a burner system according
to the invention;
FIG. 3 shows an example of a dependence of the pulsations and
emission values of a burner system according to the invention on
the fuel supply to the first stage; and
FIG. 4 shows an example of the type of operation for both stages of
the present burner system dependent on the operating load.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a single-stage burner system as known from the state
of the art, which has already been explained in the introductory
part of the specification. Compared to this system, the present
invention uses an at least two-stage burner system, as FIG. 2 shows
schematically. Like the fuel supply means 4a and 4b on or in this
swirl body 1, the conical swirl body 1 of this burner system also
is shown only very schematically. This figure shows the two stages
formed by the separate fuel supply means 4a and 4b with the
corresponding outlet openings (not shown). In each case, a notable
characteristic of this burner system, i.e., the two separate stages
along the longitudinal axis of the burner, can be seen. The burner
is followed by the combustion chamber 5 in which the
fuel/combustion air mixture produced by the premixing is burned.
The fuel is hereby supplied to the first stage 4a via fuel
distribution system 6a. The fuel supply is hereby adjusted via a
control valve 7a. In the same way, the second stage 4b is supplied
with fuel via another fuel distribution system 6b with a control
valve 7b. Both fuel distribution systems in this example are
provided separately from each other. In order to measure the
combustion pulsations, a pulsation sensor 8 that reports the
measuring values regarding the intensity of the pulsations to the
control device 10 is provided on the combustion chamber 5.
Furthermore, a sensor 9 for the emission values that also transmits
its data to the control device 10 is provided in the region of the
combustion chamber outlet. In the control device 10, the measured
data are compared with control data, and the two control valves 7a
and 7b are controlled with respect to emission values and
pulsations so as to maintain or achieve a specified operating
point.
In an advantageous embodiment, in which, for example, the first
fuel distribution system 6a directly branches off the second fuel
distribution system 6b, the control device 10 also may be used only
for controlling or regulating the control valve 7a, if the latter
is provided directly at the branching-off point. By controlling the
valve 7a, the fuel distribution to both stages then can be
influenced in the presence of a total fuel supply determined by the
control valve 7b. This simplified technique in the same manner also
enables an optimized operation of the system under different
operating and environmental conditions. In particular, such an
embodiment does not require a separate fuel supply system for the
first stage. Existing systems can be easily retrofitted using a
suitable branch-off. In addition, this internal valve 7a can be
controlled in such a way that a minimal fuel flow through the
second stage exists at any time for any operating load, so that no
flushing with inert gases is necessary. The overall control
technology is simplified by the fact that only one valve can be
controlled.
FIG. 3 shows an example of pulsations and emission values of a
burner system according to the invention as a function of the fuel
portion supplied to the first stage in relation to the overall fuel
supply. This on the one hand shows a minimum of NO.sub.x emissions,
which also contains, however, a maximum of pulsations. Such a
relationship can be established by means of prior testing. The data
for these relationships, e.g., a graph, preferably are stored in
the control device 10 or are programmed into it. The programmed
data are used by the control device 10 during operation as a basis
for deciding which fuel amounts should be supplied to the different
stages in order to maintain or achieve low emissions with low
pulsations.
The data obtained by the measuring value probes 8, 9 preferably are
compared with the stored control values by the control device's
logic in order to bring the operating point of the burner system to
the left or right side of the pulsation peak shown in FIG. 3.
During stationary operation, the left side is preferred for this
because of the low emission values. During transient operation,
where emission considerations have a lower priority than a robust
dynamic behavior of the burner, the right side of the pulsation
peak is preferred.
In this way, a gas turbine can be operated from ignition to basic
load without a separate pilot stage and only a single control
valve. FIG. 4 hereby shows an example of an operation for the case
with two stages with a stage ratio of 50% in the burner system. The
control valve hereby controls only the distribution of the entire
supplied fuel flow to both stages. While the fuel is almost
exclusively supplied to the first stage during ignition or start-up
of the burner system or gas turbine, this ratio changes by
increasing during idling, at 50% load, and 100% load. At 100% load,
the second stage is then supplied with somewhat more fuel than the
first stage. Such an operating concept makes it possible to realize
a stable operation of the burner system without an additional
requirement of a pilot stage. Naturally, the fuel distribution
shown here will be shifted by the control device during the
operation of the system in relationship to environmental conditions
and aging.
LIST OF REFERENCE NUMBERS 1 Swirl body 2 Outlet openings 3 Pilot
lance 4a Fuel supply means of first stage 4b Fuel supply means of
second stage 5 Combustion chamber 6a Fuel distribution system of
first stage 6b Fuel distribution system of second stage 7a Control
valve of first stage 7b Control valve of second stage 8 Pulsation
sensor 9 Emission sensor 10 Control device
* * * * *